1. Field of the Invention
This invention relates to fluid pressure regulating systems, such as systems for regulating the pressure of gas. The invention further relates to controlling the pressure of suction flow lines and suction chambers, and in particular as applied to wound drainage systems, for draining fluids from medical patients, such as from the chest cavity, by means of gas pressure differentials using low pressure gas systems.
2. Description of the Prior Art
In many situations involving gases, it is important, and often mandatory, to measure and regulate the pressure of the gas. In one important example, there exists in hospitals a system for distributing vacuum or suction from a central vacuum supply system, which in many cases must be monitored and regulated when it is used. These systems are used, for example, in conjunction with wound drainage devices, where fluids, such as blood and water, and gas from a wound in a patient's pleural cavity are withdrawn using a pressure differential established between a controlled suction chamber and the internal pressure in the patient. Such suction pressure and pressure differentials must be closely controlled because of the dangerous conditions which could result if unduly high or low pressure differentials should occur. In this application, as in many other pressure measuring and regulating applications, it is desirable to incorporate a pressure regulating device which is compact, which makes the pressure measurement and regulation with accuracy, which is capable of functioning reliably for long periods of time, and which is economical to manufacture.
A particularly advantageous system is disclosed in U.S. Pat. Nos. 4,698,060, 4,715,855 and 4,889,531, which are incorporated herein by reference, as well as PCT publication number WO 00/78373 A2, each of which discloses a pressure regulator and a fluid drainage system. The pressure regulator includes high and low pressure chambers separated by a divider having an opening, a closing member biased to a closing position for closing the opening with a biasing force according to a desired pressure differential between the chambers, and a damping device for damping the resulting force, and movement, on the closing member. The fluid drainage system has a suction chamber with a suction regulator and various arrangements of diaphragms for measuring pressure differentials. As economical as these systems are, they do incorporate the relatively expensive damping device, such as a dashpot, for effectively damping the force applied by the closing member in order to prevent undesirable vibration at the transition point.
U.S. Pat. No. 3,830,238, illustrates movement of a bellows assembly to detect and display the value of negativity within the pleural cavity while U.S. Pat. No. 4,468,226 discloses a bellows device which contracts as suction increases in a collection chamber. An indicator vane, connected to the bellows, moves along a fixed scale to indicate the level of suction within the collection chamber. While both of these disclosures are directed to chest drainage devices, neither of them is used to control the level of suction or negativity in the system.